Recently, the sanitary protection industry has developed improved sanitary napkins that are highly absorbent and at the same time they are thin which significantly enhances their comfort. The conventional wisdom dictates that the comfort of the sanitary napkin is directly related to its flexibility, in particular the flexibility in the lateral direction. Hence, in order to improve the comfort, sanitary napkin designers have almost universally tried to create a product which is as flexible as possible. The idea behind this approach is that the flexible product will create less discomfort to the user particularly when the sanitary napkin is compressed between the thighs of the wearer.
However, sanitary napkins that are highly flexible are known to suffer from high failure rates which can be traced to the inability of the sanitary napkin to maintain firm contact with the user's body. As a consequence, the menstrual liquid discharged cannot be captured immediately into the sanitary napkin and liquid can travel along the user's body and stain the user's undergarments or outer garments. Studies have demonstrated that sanitary napkins that are highly flexible, when placed in the crotch portion of the user and compressed by the user's thighs, deform laterally according to a random or uncontrolled manner. This results into the so-called “bunching” problem. A sanitary napkin that bunches is compressed in a way to significantly reduce its liquid absorption area and prevent close conformation with the vaginal opening. This may explain the high incidence of failure rates observed in connection with sanitary napkins that are very flexible.
One possible manner to increase the lateral rigidity of a sanitary napkin that is taught by the prior art is to calendar the napkin between a pair of rolls. This operation stiffens the entire product by the effect of compaction. A drawback of this operation, however, is to negatively affect the absorption capacity of the sanitary napkin. The compaction effectively reduces the amount of void volume in the absorptive layers of the sanitary napkin, thus reducing its ability to store liquid.
Thus, there exists in the industry a need to provide a sanitary napkin that is thin, highly absorbent and has good comfort potential and at the same time is capable of reducing the incidence of bunching in use.